Sicilians are masters of cooking eggplant, and their island home is the source of countless delicious and interesting ways to prepare it. In the past when meat was scarce, eggplant, with its meaty look and flavor, was often substituted. This recipe, named for the opera Norma, by Catania-born Vincenzo Bellini, is typical of Sicilian cooking.Salting the eggplant slices draws out their bitter juices. If the eggplant is very fresh, this step is not essential, but if you are unsure about their provenance, it is good insurance against a disappointing dish. Ricotta salata is a salted, pressed form of ricotta. If unavailable, use a mild feta cheese.